The medical label is an indispensable product identification of medicines. It can be said that it is also the ID card of medical products and an important production process in the packaging and printing process. Medical labels are printed in single-color and double-color printing, or in multi-color overprinting or overprinting; some are printed on offset paper, and some are coated on coated paper and other self-adhesive paper. From the perspective of health, safety, and anti-counterfeiting, the quality control of medical label printing is a very important technical link. The instructions for use in the product layout must be clear, legible, and easy to identify; the printed colors must meet the requirements for accuracy, purity, consistency in batches, and good anti-counterfeiting quality effects. At present, many medical labels are printed with flexible resin plates. When printing, the operation technology and process technology of the printing production process must be well controlled to improve the production efficiency and product quality of medical labels.
1 Check the technology of ink adjustment
The printing of medical labels with bright colors and uniform ink colors are the basic requirements of product quality and anti-counterfeiting technology. Therefore, how to make accurate ink preparation is a very important technical link. According to the principle of the change of the three primary colors, in addition to the gold and silver colors (the substrate is a material sprayed with aluminum paper), any color can be mixed and mixed using different proportions of the three primary colors. For example, the three primary colors of ink can be mixed into black after being mixed in the same amount. The three primary colors of ink are mixed in equal amounts and white inks of different proportions are added to form light gray inks of various shades. If the three primary color inks are mixed in various proportions, it can be blended into a variety of intermediate colors or multiple colors, but the hue is biased to the primary color hue with a large proportion. If the two primary color inks are mixed in equal amounts, they can be adjusted to the standard intermediate color; after the two primary color inks are mixed and mixed in different proportions, they can be mixed into a variety of different color hue, but the hue tends to be a large proportion of the primary color Hue. In addition, in any color ink, the hue appears brighter after adding white ink. Conversely, after adding black ink, the hue becomes darker. Whether the method of blending ink colors is appropriate will directly affect the color quality of printing. Therefore, when distributing inks, it is necessary to analyze the excellent appearance according to the original manuscript, and determine which kinds of inks should be used to dispense. For example, to adjust the lake blue ink, it can be preliminarily determined based on visual observation and practical experience. Among them, white ink is the main color, and peacock blue is the auxiliary color. It should be slightly added. As long as the main color is determined, the other colors are auxiliary colors, which should be added gradually and evenly. Then, use two pieces of paper that are the same as the printing paper? One of the paper surfaces is coated with a little adjusted ink, and the other piece of paper is used to scrape it to roughly the thickness of the printed ink layer, which is compared with the original See if it is appropriate. When comparing samples, it is necessary to scrape the ink layer on the paper where the ink layer is relatively thin and light to see it more accurately. When adjusting the ink, you should also master a principle, that is, use inks of different colors as little as possible, that is, if you can use two inks, you should not use three inks to adjust, so as not to reduce the gloss of the ink. On the other hand, the color tone of the scratched sample is slightly darker than the original color, so that the printed color sample can be accurate or close to it. After the ink tone of the sample is accurate, you can adjust the ink in batches according to their respective proportions of ink. [next]
2 Close control of printing process technology
1) Reasonably choose paper
Paper is very sensitive to changes in the temperature and humidity of the external environment. Especially the paper just produced is most prone to expansion and contraction due to changes in temperature and humidity, resulting in inaccurate product overprinting. In order to reduce the chance of this bad situation, after the paper that has just been produced is shipped back, it will generally be placed for a period of time to make the paper's characteristics relatively stable, and it will not be easy to overprint after it is put into use.
2) Reasonable arrangement of printing color sequence
Reasonable arrangement of printing color sequence is an important measure to improve printing quality. It should mainly be considered from these aspects, namely: consider the arrangement of printing color sequence according to the characteristics of the substrate; consider the arrangement of color sequence according to the differences in the structure of the printing machine; according to the print layout Consider the arrangement of the color sequence for different structures; consider the color sequence according to the color characteristics of the original; consider the color sequence according to the differences in ink characteristics; arrange the color sequence according to the drying characteristics of the ink. In this way, by scientifically and reasonably arranging the printing color sequence, the production efficiency and the printing quality of the product can be better improved.
3) Prevent the printed matter from sticking
When printing medical label products, when encountering good gloss on the paper surface; the paper is acidic (affects the drying of the ink layer); the large ink supply for printing and the slow drying speed of the ink can easily cause the back of the product to be dirty. The solution is to use the "deep ink thin printing" process for printing, that is, to adjust the ink hue a little deeper and make the printing ink layer thinner, so that it can not only meet the printing ink color requirements, but also reduce the chance of sticking. In addition, a desiccant can be added to the ink to make the ink layer dry in time.
4) Use the doctor blade properly
When printing label products with a flexo printing machine, the doctor blade is an important part of the printing machine to maintain uniform and suitable ink delivery, and is also a control condition that can not be ignored. The squeegee and ceramic anilox roller are matched to form an ink transfer system, which generally uses a plug-in reverse squeegee structure, which has the advantages of convenient operation and uniform ink scraping. The material of the squeegee is usually two kinds of steel sheet and plastic sheet, and the blade edge is planed into a slope, which is convenient for uniformly scraping ink and controlling the amount of ink transfer. The correct adjustment of the doctor blade pressure is very important. The correct adjustment of the doctor blade pressure should be based on the scraping of excess ink on the surface of the anilox roller.
5) Determine ink viscosity according to printing speed
Due to the "thixotropic" characteristics of the ink, the viscosity of the ink should be determined according to the area of â€‹â€‹the printing plate and the speed at the time of printing. The flexo printing process is generally controlled between 40 ~ 50s. However, since the temperature when ink is used varies from place to place, which will affect the viscosity and printing effect of the ink, it should be scientifically controlled and adjusted according to the printing environment.
6) Pay attention to storing ink
The ink should never be placed in an open air environment. The temperature for storing ink should be around 20 â„ƒ. Any unused ink should be put back in the barrel and kept in a cool and closed place. [next]
7) Pay attention to the ink shelf life
The shelf life of general ink is about 12 months, while the shelf life of gold ink is half a year, or even less than half a year. Therefore, according to the production situation, we must purchase the ink brand and quantity suitable for the characteristics of the product to ensure the printing quality of medical label products.
8) Prevent excessive foaming of ink
If more ink appears in the flexographic printing process, it is easy to affect the quality of the printed product. A small amount of defoamer can be added to eliminate the foam. The amount of defoamer should be controlled within 0.2% of the amount of ink.
9) Control and adjust the feeding force
It is very important to control the tension of the unit-type web flexo printing machine, because the flexo printing machine is a rotary machine that uses continuous feeding for printing or glazing, die-cutting mechanical structure. When the tension is unbalanced or not When it is stable, it will easily affect the overprint accuracy of the label printing layout, affect the label printing quality at least, and cause the waste of base paper. Therefore, pay attention to control the tension during printing, keep it accurate and constant during the printing process, and ensure the stability and balance of the paper feeding on both sides. This is an important control link to ensure the accuracy of label overprinting.
10) Control the inking pressure of flexo printing
The control of the inking pressure should be based on the characteristics of the printed layout. Generally speaking, the pressure of the printed screen, small reverse white text, and small line layout can be slightly higher; the pressure of the field layout and the line layout with larger area can be adjusted relatively. Smaller to increase the amount of ink coating to ensure the saturation and brightness of the printed color.
11) Control the ink transfer pressure of flexo printing
The pressure between the anilox roller and the plate roller also affects the printing quality. If the pressure is too heavy, it is prone to the defects of plate printing deformation, dot expansion, paste printing, and reduction of the printing plate resistance. If the pressure is too light, if the amount of ink on the printing plate is insufficient, there will be ills such as unclear imprints and flowering on the printing plate. The adjustment of the ink transfer pressure should be balanced by the pressure on both sides of the anilox roller and the plate roller, so that the ink transferred by the anilox roller can be uniformly obtained on the plate roller.
12) Control the printing pressure of flexo printing
If the pressure between the plate roller and the platen roller is too large or too small, it is easy to affect the printing quality of the product. The printing pressure adjustment of flexo printing is to maintain a moderate contact condition between the plate roller and the platen roller, so that the ink layer on the plate is evenly transferred to the substrate, and the color of the printing ink is saturated and the imprint is clear. [next]
3 Control the printing quality of flexographic dots
If the production process is not properly controlled for medical label products with layout dot structure, quality problems such as dot loss and deformation expansion are prone to occur. For example, small dots in the highlight part of the layout are easy to be lost, and the dark tone dot parts are prone to enlarge and paste and become like of. Due to the expansion and deformation of the dots, the print layout lacks a sense of hierarchy, and the quality of the printing copy is significantly reduced. The printing plate material is soft and elastic, which is the main reason why the flexographic printing dots are prone to quality problems. Process analysis shows that in the flexographic printing process, under the action of pressure, the size of the printing plate becomes larger, so that the dot area becomes larger, and small dots are easy to be lost due to wear or uneven pressure. On the other hand, due to the use of low-viscosity inks for flexographic printing, when the contact pressure between the surface of the printing plate and the printed product is slightly higher, the ink on the printing plate will spread outward, making the middle layer of the expanded dot thin The ink layer at the edge is thick, forming a hollow-like dot. When the magnifying glass is used to observe, the dot edge can be seen to be pasted. This is the basic feature of the increase of the dot of the flexographic printing. The production process also shows that the higher the dot line number of the flexible version, the greater the dot increase value; the thicker the particles of the ink used, the greater the dot expansion; the larger the amount of ink in the layout, or the ink is too thin, the dot expansion The greater the printing pressure and the anilox roller pressure, the greater the dot expansion; the softer the substrate, rubber roller, liner or flexographic plate, the greater the dot expansion; the aging of the machine so that the accuracy is worse, the dot expansion The bigger. In addition, the thickness of the printing plate is inconsistent, and it is easy to make the printing dots expand or lose. Therefore, to prevent the occurrence of printing quality problems of flexographic dots, we must pay attention to the good process technology and operation technology, and also choose the high-quality and high-precision plate materials. At the same time, we must pay attention to the maintenance of equipment to be better. Ensure the printing quality of outlet products.
4 Prevent the loss or deformation of flexographic dot printing
In the printing production process, if the production process is not properly controlled, quality problems such as dot loss and deformation expansion are prone to occur. For example, small dots in the high-gloss part of the layout are easy to be lost, and the dark-tone dots are prone to expand and paste and become like the ground. Therefore, the flexographic printing process is difficult to express the dots below 5%, and the dots above 95% are easily pasted together, and the middle and dark tone parts are easily lost. At the same time, due to the ductility of the flexible plate, it is difficult to improve the accuracy of plate overprinting. Due to the expansion and deformation of the dots, the print layout lacks a sense of hierarchy, and the quality of the printing copy is significantly reduced. It can be seen that the printing plate material is soft and elastic, which is the main reason why the flexographic printing dots are prone to quality problems. The process analysis shows that during the flexographic printing process, under the action of pressure, the graphic size of the printing plate becomes larger, which tends to make the dot area larger, and the small dots are easy to be lost due to wear or uneven pressure. On the other hand, due to the use of low-viscosity inks for flexographic printing, when the contact pressure between the surface of the printing plate and the printed product is slightly greater, the ink on the printing plate will spread outward, making the middle ink layer of the expanded dot thin. The ink layer on the edge is thick, forming a hollow-like dot. When the magnifying glass is used to observe, the dot edge can be seen to be pasted. This is the basic feature of the increase of the dot of the flexographic printing. The production process also shows that the higher the dot line number of the flexographic version, the greater the dot increase value; the thicker the particles of the ink used, the greater the dot expansion; the greater the amount of ink in the layout, or the ink is too thin, the dot expansion The greater the printing pressure and the anilox roller pressure, the greater the dot expansion; the softer the substrate, rubber roller, liner or flexographic plate, the greater the dot expansion; the aging of the machine so that the accuracy is worse, the dot expansion The bigger. In addition, the thickness of the printing plate is inconsistent, and it is easy to make the printing dots expand or lose. Therefore, to prevent the occurrence of printing quality problems of flexographic dots, a better solution is to pay attention to the maintenance of equipment, choose high-quality, high-precision plates and high-quality inks, and pay attention to good operation techniques. Off and printing technology. When the printing unit is redundant, when printing the screen version of the screen version and the field version, you should consider separating the screen version and the field version and printing separately. This is not only conducive to the accurate control of the printing pressure, but also to the ink. Uniform coating to improve the printing quality of flexo products. [next]
5 Prevent and eliminate ink stick phenomenon on the label product layout
When the thickness of the printing plate is uneven or the double-sided tape at the bottom has wrinkles, the old version should be replaced with high-precision high-quality materials or the double-sided tape on the back of the plate should be re-attached to eliminate wrinkles.
When the squeegee is improperly installed or the fastening device is loose, the squeegee should be reinstalled and the squeegee should be re-fastened to prevent the squeegee from moving.
When the ink fountain roller and the anilox roller are partially worn out, new ink fountain roller and anilox roller should be replaced. In normal operation, care should be taken to prevent dry friction of the roller body, and the amount of ink must always be sufficient. In the absence of ink, the squeegee or ink fountain roller and the anilox roller body should be kept in tight contact and rolling.
When the anilox roller has ink drying on some of the cells, the anilox roller should be thoroughly cleaned to effectively remove the accumulated ink in the cells.
When the engraved anilox roller mesh holes are arranged incorrectly or the anilox roller mesh holes have linear scratch marks, the anilox roller should be replaced and reprocessed.
When the particle impurities in the ink are stuck in the doctor blade or the anilox roller cavity, the ink impurities in the doctor blade should be removed or the fine ink should be replaced for printing. In addition, when using old ink, it should be filtered before use.
In summary, improving the printing quality of medical product labels is the basic requirement for product usage characteristics. Medical product labels with good printing quality can give people a sense of credibility and security when they are used. Therefore, correctly understand the printing technology control technology of medical product labels and adopt advanced technical measures to control the printing process, which can not only effectively Prevent the occurrence of various printing defects, and can better improve the printing production efficiency and product printing quality.
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